Non-thermal atmospheric pressure ('cold') plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O 2 , N 2 , air, H 2 O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of 'high' voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.
The VUV-absorption spectroscopy (AS) and the emission spectroscopy (ES) from delocalized probe plasma, are implemented in the downstream chamber of a soft-etch industrial plasma reactor. A CCP plasma, running in the upper compartment in He/NF3/NH3/H2 mixtures at about one Torr, produces reactive species which flow through a shower head into a downstream chamber, where they can etch different µ-electronics materials: Si, SiO2, SiN,... The ES reveals the presence of F and H atoms, while the dissociation rates of NF3 and NH3 are deduced from the AS, as well as the density of HF molecules, produced by chemical chain-reactions between dissociation products of NF3, NH3 and H2.
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